1. Field of the Invention
The present invention relates to an impact dot printing head control apparatus for driving an impact dot printing head.
2. Discussion of the Background
An impact dot printing head is a device for printing by causing armatures linked with wires for printing, respectively, to rock between a printing position and a standby position, and by causing the respective tips of the wires to collide against a printing medium such as paper for printing when the armatures are caused to rock to the printing position. The impact dot printing head is provided with a plurality of the armatures. Consequently, there exist as many wires as the armatures. The number of the wires, in common and widespread use at present, is from 24 to 48.
The characteristics of the impact dot printing head, such as impact force, the maximum response frequency, and so forth, change depending on a use environment. In particular, in case the use environment is at low temperature, there can be a case where the wire in printing operation is subjected to considerable resistance caused by a lubricant, such as grease etc., applied between wire guides supporting the wire and the wire. As a result, impact force characteristics undergo a change. Accordingly, various methods have so far been proposed as a method of driving the impact dot printing head. For example, with a method disclosed in Japanese Patent Publication No. 2878433, a given impact force is obtained by rendering a driving condition variable in response to variation in temperature with the use of impact force variable means in order to ensure the performance of an impact dot printing head against variation in temperature. In particular, under conditions where the performance of the impact dot printing head deteriorates, large energy is applied to the impact dot printing head temporarily with the use of the impact force variable means.
In the case of ensuring the performance of the impact dot printing head by rendering, for example, current variable as in the past, the wire is driven by supplying current at 1.2 A per one wire at the time of normal temperature, and at 1.4 A per one wire at the time of low temperature. Accordingly, in the case of the impact dot printing head having 48 wires, an instantaneous current value will be 57.6 A at the time of normal temperature, and 67.2 A at the time of low temperature, resulting in a difference of as much as 9.6 A. Consequently, a large power source needs to be prepared to meet requirements for driving the wires at the time of low temperature. Further, the specification of driver elements for the impact dot printing head also needs to be enlarged. As a result, there will be an increase in product cost, and it has been difficult to implement downsizing of a product.
It is therefore an object of the invention to implement reduction in product cost and downsizing of a product while ensuring the performance of an impact dot printing head even at the time of low temperature.
The object of the invention is attained with a novel impact dot printing head control apparatus according to the invention.
Accordingly, in the novel impact dot printing head control apparatus according to the invention, a normal fire is generated which drives respective wires of the impact dot printing head so as to reach a printing position on the basis of printing data and a driving frequency of the impact dot printing head, and prior to the normal fire, a pre-fire is generated which drives the respective wires so as not to reach the printing position, whereby the drive control of the respective wires is implemented on the basis of the normal fire and the pre-fire.